Electronic structure and stability of intermetallic compounds in the Ti-Ni System

For the systematical understanding of the stability of martensitic phases and precipitates which appear in Ti-Ni shape memory alloys, we made a first principle electronic structure calculation of them by using the tight-binding linear muffin;tin orbital method in the atomic sphere approximation (TB-LMTO-ASA). The obtained results are the following: (I)the total electronic density of state (DOS) at the Fermi energy D(epsilon(F)) of TiNi decreases as the successive B2 --> R --> B19' transformation proceeds; (2) when the number of valence electrons increases, D(epsilon(F)) of the R-phase increases but that of the B19-phase decreases; (3) D(epsilon(F)) of Ti(3)Ni(4) decreases as the number of valence electrons decreases and that of TiNi, decreases as the number of valence electrons increases. By comparing these results with experimentally obtained results, we derived a criterion that phases appearing in Ti-Ni system tend to become stable at 0 K as D(epsilon(F)) decreases. (C) 1999 Elsevier Science S.A. All rights reserved.